If a converged solution from springback prediction cannot be obtained after trying many different combinations of parameters, what else can I do?

Use dynamic relaxation method. Usually this is not necessary. For most
of the application jobs, converged solutions can be obtained if the
jobs are set up properly.

If the part is very flexible, it is possible that convergence is
difficult to get with implicit method. However, dynamic relaxation
method is time-consuming, and it is should be used only when explicit
method fails.